1. Field
Embodiments of the present invention relate to the field of power delivery for computing devices and more specifically to adaptive power delivery to control and manage power efficiency for one or more devices in a system.
2. Discussion of Related Art
A typical example of a power delivery network is shown in FIG. 1. A hard disk drive (106) is directly powered by a voltage regulator (104). The voltage regulator converts the system supply voltage (102) to the appropriate voltage level (Vcc) required by the hard disk drive under its entire load current range (Icc).
Power consumption of a hard drive varies from time to time during its operation. Table 1, below, illustrates the power consumed during various stages of operation by a 1.8 inch Toshiba® MK2004 hard disk drive requiring a supply voltage of 3.3V±5%:
TABLE 1Power consumption of a hard disk driveOperating ModeAverage PowerStart1.2 WSeek1.4 WRead/Write1.4 WActive Idle0.6 WLow Power Idle0.4 WStandby0.2 WSleep0.08 W 
Even though the drive operates at a single fixed voltage level, its load power or current changes by approximately 2× from the start mode to active idle. There is nearly a 10× change in power consumption from active idle mode to sleep mode.
A typical voltage regulator (104) may be designed to optimize its performance at a single maximum load point, Icc_MAX. Thus, for all other operating loads, the performance of the voltage regulator may be less efficient. Typically the efficiency of the voltage regulator is 30-50% less at a light load (e.g. less than 10% of Icc_MAX).
FIG. 2 is a graph (200) illustrating the power efficiency of an example voltage regulator across a range of load currents. The example voltage regulator is most efficient at the maximum load current, Icc_MAX, and is less efficient at loads less than Icc_MAX. Region 202 indicates a region of lower load current operation, such as in the active idle, low power idle, standby, or sleep modes, where power efficiency may be lower than the maximum efficiency. Thus, in some modes there may be power loss caused by the inefficiency of the VR, which can lead to shorter battery life in a battery powered system.